package app

import (
	"fmt"
	"os"
	"strings"
)

const tabBarRows = 1

// drawTabBar renders SPEC §4's top tab bar at row 1. Tabs are top-level
// children (ParentID == ""); the focused tab is highlighted. The PTY
// region begins at row 2.
func (st *uiState) drawTabBar() {
	st.mu.Lock()
	palOpen := st.palette != nil
	focus := st.focusedID
	st.mu.Unlock()
	if palOpen {
		return
	}
	layout := st.layoutSnapshot()
	width := int(layout.childCols())

	var sessions []*Child
	for _, c := range st.sess.Children() {
		if c.ParentID == "" && c.Status() == StatusRunning {
			sessions = append(sessions, c)
		}
	}

	var b strings.Builder
	b.WriteString("\x1b[1;1H")
	cur := 0
	for _, c := range sessions {
		label := c.Name
		seg := " " + label + " "
		if cur+len(seg) > width-2 {
			break
		}
		if c.ID == focus {
			b.WriteString("\x1b[7m")
		} else {
			b.WriteString("\x1b[2m")
		}
		b.WriteString(seg)
		b.WriteString("\x1b[0m")
		cur += len(seg)
	}
	// "+" hint at end.
	hint := "+"
	if cur > 0 {
		hint = "  +"
	}
	if cur+len(hint) <= width {
		b.WriteString("\x1b[2m")
		b.WriteString(hint)
		b.WriteString("\x1b[0m")
		cur += len(hint)
	}
	// Fill the rest of the tab-bar row so stale chars don't linger.
	if width-cur > 0 {
		b.WriteString(strings.Repeat(" ", width-cur))
	}

	st.outMu.Lock()
	defer st.outMu.Unlock()
	// Save cursor, paint, restore.
	fmt.Fprintf(os.Stdout, "\x1b7%s\x1b8", b.String())
}